1. Field of the Invention
The present invention relates to an organic light emitting display (OLED) device and, more particularly, to a system on panel (SOP) type scan driver which generates scan signals for selecting pixels located on a display region, and an OLED device having the same.
2. Description of the Related Art
Recent years have seen considerable research into flat panel displays (FPDs) because they can be made smaller and lighter than display devices using cathode ray tubes (CRTs). As a result, liquid crystal displays (LCDs), field emission displays (FEDs), plasma display panels (PDPs), and organic light emitting displays (OLEDs) have been developed and put to practical use. Among these FPDs, the PDP can have a large screen but has low luminance and poor luminous efficiency resulting in high power consumption, and the LCD has a relatively slow response speed and consumes a lot of power since it employs a backlight.
However, as the OLED makes use of an organic material to emit light, it has a wider viewing angle and faster response speed than the LCD. Also, the OLED is an emissive display that obtains good contrast and visibility. Further, the OLED enables lower power consumption and can be made thin and lightweight because it needs no backlight.
Nevertheless, the dimensions of an electroluminescent (EL) panel for a glass substrate are limited due to fabricating process limitations and the OLED may not be easily constructed to have a large screen. Also, if the screen is large, there is a greater probability of a defect occurring somewhere on the screen and thus a reduction in yield is unavoidable. Further, it is difficult to obtain uniformity across the screen.
As a solution to the above problems of the OLED, a tiling technique was developed. In the tiling technique, EL panels are bonded together like tiles to form a single panel.
Each of the EL panels includes pixels to display a predetermined image similar to a conventional OLED. In each of the EL panels, a scan driver applies a scan signal to enable the pixels, and a data driver applies a data signal to a selected pixel. Also, an emission control driver applies an emission control signal to each of the pixels in order to control the exact programming of the data signal and the time taken for an emission operation.
As described above, the scan driver, the data driver, and the emission control driver, which transmit various signals to drive the EL panels, can be electrically coupled to each of the EL panels in various manners.
For example, the scan driver, the data driver, and the emission control driver may be mounted as chips on a tape carrier package (TCP) that is bonded and electrically coupled to each of the EL panels. Alternatively, the drivers may be mounted as chips on a flexible printed circuit (FPC) or a film that is bonded and electrically coupled to each of the EL panels. The latter technique is referred to as a chip on flexible board (or chip on film) (COF) technique. In another method, the drivers are directly mounted on a glass substrate of the EL panel. This method is referred to as a chip on glass (COG) technique. These methods are costly and only complicate the modules, because the drivers should be separately designed and electrically coupled to one another.
To overcome these drawbacks, a system on panel (SOP) technique has been developed recently. Also, there have been attempts at designing a display region, scan and emission control drivers, and/or a data driver in each EL panel, in order to include all parts of the system in each of the EL panels.
In the OLED using the tiling technique, when each EL panel is formed as an SOP, it is easy to bond the EL panels to one another. Also, the SOP technique enables the area of drivers to be reduced and cost and labor for designing integrated circuits (ICs) of the respective drivers to be saved.
However, in order to develop the SOP-type OLED, it is necessary to consider many internal circumstances and conditions of the EL panels, such as a driving frequency and electron mobility of the data driver and/or the scan and emission control drivers. Up to present, it has been difficult to design the data driver within a panel because the data driver needs a high driving frequency.
Accordingly, the data driver is formed separately as an IC using complementary metal oxide semiconductor (CMOS) technology and subsequently coupled to the EL panel, while the scan driver and/or the emission control driver are formed within the EL panel.
Therefore, there is a need for a simple circuit construction in which an SOP-type scan driver and emission control driver can be optimally driven in the EL panel.